Drugs are useful in elucidating the mechanisms and functions of brain monoamines, including their role in several models of behavior. Animals with brain amines altered by drugs (including intraventricular 6-hydroxydopamine alone or in combination with desmethylimiprimine and D-amphetamine, reserpine, lithium, and phenoxybenzamine)or by stereotaxic lesions (of locus coeruleus and dorsal ascending bundle) will be tested for conditioned avoidance behavior, locomotor activity, and shock-induced aggression. A new microdissection technique will be used to remove discrete brain regions, and catecholamines and related synthetic enzymes will be assayed by sensitive radioisotopic methods. Performance on behavioral tests will be correlated with biochemical changes in specific brain regions. The cholinergic adrenergic interaction will be examined by measuring the activity of choline acetyltransferase in discrete brain regions after alterations of brain monoamines produced by drugs or by stereotaxic lesions.